The present invention relates in general to bodily electrical signal monitors, and more particularly to a monitor and method for acquiring and processing EEG data in EEG monitors.
An EEG data signal is an acquired medical electrical signal representing brain activity. The EEG data signal is in the form of complex waveforms which can be broken down into a series of sine waves. The frequencies and amplitudes of each of these sine waves are analyzed to represent the bioelectrical activity of millions of neurons in the brain. During an operation, anesthetics, neuroactive drugs, ischemia or other physiological changes in the brain are monitored by examining the EEG data. Recently, bispectral analysis of EEG data has been used to derive more complete information concerning such physiological changes. However, during use of existing EEG monitors, noise may obscure or distort the original EEG data signal.
To the naked eye, an EEG data signal looks to be significantly affected by noise, and very heavy filtering is commonly used to preserve the important characteristics of the EEG data signal. In prior art systems, filtering is often not successful because of artifacts such as electrocautery which generate noise over a wide band including the band of interest in the EEG signals. It is frequently difficult or impossible to differentiate the artifact signal in the EEG band from the EEG itself. This can lead to a situation where the artifact is mistaken for an EEG, and possibly to a misdiagnosis.
Another problem often encountered with known signal gathering devices which are connected through wires or cable to a monitor is that electrode leads will often be disconnected without the monitor accounting for the missing signals. This can lead to the production of false or misleading results which could cause further medical problems.
It is therefore a principal object of the present invention to provide a monitor and method of acquiring and processing EEG data which provides improved signal quality.
Another object of the present invention is to provide a monitor for acquiring and processing EEG data that is highly impervious to electrical noise pollution in the operating room.
It is also an object of the present invention to provide a monitor for acquiring and processing EEG data that has a portable data acquisition module with very low power requirements.